Fluid displacement pumps provide fluid at a volume flow rate that is proportional to the rotational speed of a pump input member. The fluid volume pumped per input member revolution is substantially constant. As such, the pump outputs a relatively high volume flow rate when the rotational speed of the pump input member is high. Depending on the application of the pump, an output volume flow rate greater than a desired flow rate may be provided.
In particular, many internal combustion engines are equipped with lubrication pumps to provide pressurized lubricant to one or more moving components. Typical lubrication pumps are sized to provide a maximum output pressure at a predetermined operating speed. Many vehicle engines are rarely operated at maximum speed where maximum pump output is required. The engine frequently operates at lower rotational speeds. At the lower engine speeds, the pump output may be greater than required. A higher output pressure is maintained than necessary. An inefficient conversion of energy to heat may result thereby reducing the efficiency of the engine and pump combination. While many lubrication pumps are equipped with a pressure relief valve to assure that a maximum pressure within the lubrication system is not exceeded, these simple systems do not address the need for a reduced pump output at low to moderate engine operating speeds.
Some engine lubrication systems attempt to include components to reduce the pump output in the low to moderate engine speed range of operation. The previously known arrangements, however, may include high cost solutions incorporating multiple relief valves, solenoids and other control hardware. As such, it may be beneficial to provide a simplified pressure relief valve for increasing the energy efficiency of a pump.